For real estate, I would choose a subniche where you take gorgeous content (photos or videos) of dream like homes (or before and afters of non-renovated/staged to renovated/staged) where your primary point is to build a follower base for exposure, NOT to directly sell what is in your content. This obviously requires somehow building the content creation component into your house selling process and needs consistent and frequent posts.
After that, giveaways and sweepstakes (for example, Home Goods/Bed, Bath, and Beyond Gift Cards) where people follow and tag a friend to win. Sponsored ads, etc. Once it has built up a good reputation, figure out how to funnel that into a place where you can convert it to actual sales.
There are a few things you can do to figure out if someone is legit or not—for example if you have barely any content but suddenly gain a lot of followers for no apparent reason, that’s a good sign someone is purchasing followers/engagement.
Social media marketing takes a LOT of work depending on what you want your social media marketer to do, whether they are capable of doing it, or will you need other specialists. There are some who are able to give you the whole package of photography/videography, curating content, editing content, posting content, and managing it, but those are big $$$ and often firms rather than individuals. (Although it IS possible for individuals but those individuals likely are doing and promoting their own content already.)
Anyway, hope this helps.